Repro 6 and 7 Flashcards
Maternal recognition of pregnancy in Horses caused by:
- not fully understood BUT mobility of embryo is v important
Maternal recognition of pregnancy in primates caused by:
- Gonadotropin
What needs to be STOPPED in order to allow pregnancy?
- Luteolytic signal
- What hormone is essential for pregnancy?
- What secretes it?
3 and 4. Takes a while to secrete so what happens?
- Progesterone
- Placenta secretes
- Takes while before placenta developed sufficiently to secrete enough progesterone sooooo
- Progesterone from corpus luteum can provide progesterone
How do cows and sheep recognise pregnancy?
- The blastocyct produces interferon which blocks synthesis of oxytocin receptors
- This prevents oxytocin releasing PGF from the endometrium
Finding maternal recognition tricky so gover
qqq
Time of placenta attachment in cow sheep mare sow
Most species 21 days, mare later, sow earlier
- cow = 18- 22 days
- Sheep = 15-18 days
- Mare 36- 38 days
- Sow = 11-12
When does most pregnancy loss occur in dairy cattle?
- in first few weeks when maternal recognition of pregnancy and placental attachment is occuring
xxx Describe the form & extent of placental
attachment in the main domestic species
Explain how the extra-embryonic tissues form the
placenta
- What are the three types of embryo tissue
- What form from?
- What do they go on to form
- Endoderm, Mesoderm, Ectoderm (outer)
- form from inner cell mass of blastocyst
- Endoderm = digestive system, lungs, endocrine sysmte
Mesoderm = muscle, skeleton, cardiovascular, reproductive system
Ectoderm = Nervous system, skin, hair
What are the two layers called that protect the embryo and what is inbetween these?
- Embryo, fluid, amnion, fluid, allantochorion
What does embryo develop from from blastocyst?
INNER CELL MASS
Role of placenta
- provides an interface for metabolic exchange between dam and foetus
- Transitional endocrine gland producing hormones to: maintain preg, stimulation of maternal mammary gland, promotrion of foetal growth
What type of placenta do cow and sheep have?
- Cotyledonary placentas = numerous, discrete, button like structures called cotyledons.
- Cow = CONVEX
- Sheep = CONCAVE
What type of placenta do cow and sheep have?
- Cotyledonary placentas = numerous, discrete, button like structures called cotyledons.
- Cow = CONVEX
- Sheep = CONCAVE
Membrane of fetus not attached all way across uterus
What type of placenta do cow and sheep have?
- Cotyledonary placentas = numerous, discrete, button like structures called cotyledons.
- Cow = CONVEX
- Sheep = CONCAVE
Membrane of fetus not attached all way across uterus - 6 layers
What type of placenta pig adn horse
- Diffuse placenta = membranes of foetus attached all way across uterus
- Uniform distribution of chorionic villi
- 6 layers
Placenta of dog and cat
- Zonary placentae
- Band like zone of chorionic villi attachment to mum
- 5 layers
Layers
- outer = atlant coria
- allantoic fluid
- amnia
- amniotic fluid
In early embryo how do gonads develop?
- Primordial cells migrate from yolk sac into gonadal ridge.
- Gonad is bi potential
- local tissue differentiate into sex cords
How is sex determined?
- determined by gene on sex chromosome
What happens if male (XY)
- SRY protein development
- protein causes testes to develop
- sertoli cells secrete antimullerian hormone (AMR) and dihydrotestosterone
- 2 hormoens drive development of male duct system
- AMH = degenerates structure called paramesonephric duct
- dihydrotestosterone = differentiation of doetal leydig cells = testosterone = development of male duct system
Development of female (XX)
- No SRY protein
- No AMH
- Paramesonephric ducts become ovaries, uterus, cervix and vagina
Importance of developing XX and XY twins in calves
- Testis develop BEFORE ovaries
- In cattle, fusion of outer membranes (atlantocorian) = fusion of blood supply
- Testis develop first, secrete AMH adn testosterone
- If female calf other twin can cause degeneration of female twin
- Female 99% change sertile
Importance of developing XX and XY twins in calves
- Testis develop BEFORE ovaries
- In cattle, fusion of outer membranes (atlantocorian) = fusion of blood supply
- Testis develop first, secrete AMH adn testosterone
- If female calf other twin can cause degeneration of female twin
- Female 99% change sterile.
- Diagnose = short vagina = Free martin
Describe anatomy of the umbilical cord
- 2 umbilical arteries (thicker wall)
- 1 umbilical vein (ruminants branches)
- 1 uranchus (allantoic duct) continuous with foetal bladder
Describe the arrangement of the 2 umbilical arteries
- blood pumped by fetal heart to mum.
- From heart, aorta, at base of aorta = illiac artery branch into internal and external. 3. Umbilical arteries come off internal illiac.
- Run close to lateral sides of bladder.
- Coil around umbilical vein. Towards placenta, branches = capillaries = point where placenta meets mum
What do umbilical arteries connect?
- Left and right internal iliac arteries to foetal maternal blood exchange at the chorionic villi
What do umbilical vein connect
- Foetal maternal blood exchange at the chorionic villi to ductus venosis and vena cava
What does the Urachus connect?
- Bladder to allantoic cavity
What do the vessels of the umbilical cord become once born?
- UA = round/ lateral ligaments of the bladder
- UV = the round ligament of the liver
- Urachus = scar on bladder
What do the vessels of the umbilical cord become once born?
- UA = round/ lateral ligaments of the bladder. Arteries retract
- UV = the round ligament of the liver
Close and temporarily remain outside body - Urachus = scar on bladder
Close and temporarily remain outside body
If got an animal with naval infection how can you decide if its the umbilical vein or urachus that is infected if only one?
- UV = cranially towards liver
2. Urachus = caudally towards bladder
Rough Endocrinology of pregnancy early to late
- Progesterone produced by corpus luteum in early pregnancy
- Placenta secretes progesterone
- Progesterone levels shoot up high in early and then fall rapidly at partuition
Rough Endocrinology of pregnancy early to late cow
- Progesterone produced by corpus luteum in early pregnancy
- Placenta secretes progesterone
- Progesterone levels shoot up high in early and then fall rapidly at parturition
What does the placenta in the mare produce?
- Produces Equine chorionic gonadotrophin (eCG) by endometrial cups
- eCG produces luteotropin whihc helps maintain corpus luteum on ovary and stimulates formation of accessory CLs
What is the outside foetal membrane called?
Atlantochorian
How does the progesterone concentration vary in the mare gestation?
- Inc from day 0 as primary corpus luteum secretes
- Primary CL and eCG so inc progesterone
- about day 100 placenta produces majority of pogesterone
- Conc increases at each step then starts to dec until partuition
Progesterone hormones in bitch
- corpus luteum provides all progesterone needed for all pregnancy
- placenta not produce much progesterone at all!
How does the importance of the corpus luteum vary between species?
Why is this important to know
- Bitch vvvvv important during all gestation
- cow stops important between month 6 and 8
- If want to terminate a pegnancy
If pregnancy is dependent upon progesterone coming from the CL how terminate a pregnancy?
- Possible to terminate by getting rid of corpus luteum
- Horse = CL important until 70 days. Placenta at 100 days so slight gap where could terminate but not 100%
- dogs and cats pigs and goat. terminate preg all way though as CL important all way through
- Cow up to 6-8 months as this is when CL important
What initiates parturition hormoanlly
- progesterone falls
2. oestrogen peaks
How does the peak in oestrogen at parturition differ to the peak at estrus?
At parturition the peak is wayyyyyyyyyyyyyyyyyyyyy higher than estrus as placenta produces a lot a lot of oestrogen.
All species pretty low adn then huge peak. Horse high at parturition but inc after estrus and peaks late pregnancy
What initiates parturition?
- foetal mass
- mature enough that hypothalamus, pituritary gland and adrenal gland are ready to go
- placenta has limited amount of oxygen, nutrient adn waste product exchange
- inc fetal stress as more squashed and too big for placenta
- initiation of HPA axis and release ACTH (anterior pit), cortizol fetal adrenal, stress hypothalamus.
What does fetus need to be
- alive to release hormoens
- if dead, infection and irritation initiates parturition
- If dead and no infection it would stay forever
Why do animals with twins have an shorter gestation?
- fetal stress kicks in earlier as less space/ exchange
How the foetus initiates aprturition basic
- Inc foetal stress: overcrowding, less exchange
- Inc foetal ACTH due to hypothalamic hormone
- Inc foetal cortizol which is fat soluble so can spread to mom. Casues enzymes in placenta to produce oestradiole and stop progesterone. Also inc in progtroglandid F 2 alpha = relax pelvic ligament
How does the release of prostoglandin F 2 alpha initiate parturition?
- cuases luteolysis = no progesterone form corpus luteum
2. Inc myometrial contractions leads to positive feedback
How does the release of oestradiole initiate parturition?
- Inc secretion by in tract = lubrication
2. inc myometrial contractions. leads to positive feedback
What are the 3 stages of parturition?
- Stage 1 (longest by far) = initiation of myometrial contractions and cervical dilation
- Stage 2 = expulsion of foetus
- Expulsion of foetal membranes
As soon as fetus enters vagina what 2 reflexes occur?
- spinal reflex: sensory receptors in vagina = physically causes abdominal straining
- Neuroendocrine reflex releasing oxytocin
What reflex accelerates parturition?
- Ferguson (neuroendocrine)
- fetus into cervix = sensory receptors
- impulses via nerves to dorsal root ganglion
- spinal cord to hypothalamus: paraventricular nucleus which produces oxytocin
- Posterior pit releases oxytocin
- target receptors = myometrium
- causes smooth muscle of myometrium to contract
- further into cervix = more sensory info = positive feedback
- OXYTOCIN is important in parturition but DOESN’T INITIATE!!
